Tunable inductor arrangement, transceiver, method and computer program

ABSTRACT

A tunable inductor arrangement arrangable on a chip or substrate is disclosed. The tunable inductor comprises a first winding part connected at one end to a first input of the tunable inductor arrangement, a second winding part connected at one end to the other end of the first winding part, a third winding part connected at one end to a second input of the tunable inductor arrangement, a fourth winding part connected at one end to the other end of the third winding part, and a switch arrangement arranged to tune the tunable inductor arrangement. Tuning is performed by selectively provide any of a circuit comprising the first and third winding parts in series between the first and second inputs, or a circuit comprising the first, second, fourth and third winding parts in series between the first and second inputs. The first and third winding parts are arranged on the chip or substrate such that magnetic fields of the first and third windings are essentially common, and the second and fourth winding parts are arranged to cancel electro-magnetic coupling with the first and third winding parts. A receiver, transceiver, communication device, method and computer program are also disclosed.

TECHNICAL FIELD

The present invention generally relates to a tunable inductorarrangement, a radio frequency transceiver or receiver with a resonatorhaving such an arrangement, a communication device, a method of tuningthe arrangement and a computer program for tuning.

BACKGROUND

As more bands are to be supported in radio transceivers, which bands mayspan over a wide frequency range such as from 700 MHz to 3800 MHz, thiscan be met by a set of resonators. It is known that tuning an LC(inductor-capacitor) resonator more than one octave is difficult, whichgives that a multitude of resonators may be demanded. This problem isfurther emphasized when carrier aggregation, i.e. the communication isperformed on several different carriers simultaneously, which carriersmay be spread anywhere in the wide frequency range.

LC resonators consume chip space, when implemented on-chip, and arefairly costly when implemented off-chip. It is therefore a desire toprovide more flexible resonators.

SUMMARY

An object of the invention is to at least alleviate the above statedproblem. The present invention is based on the understanding that bothcapacitance and inductance of an LC resonator need to be tuned toachieve the desired flexibility. A tunable inductor arrangement isprovided accordingly. The inventor has also realized the demands thatthe self-resonant frequency need to be set high enough forhigh-frequency modes, the Q-value has to be high enough, particularly inlow-inductance state, not to degrade gain or increase currentconsumption in a usable implementation, and that the ratio of theinductances need to be high enough to also cover the low bands. This isachieved by a switch arrangement in the tunable inductor arrangementwhich performs signal routing such that insertion loss is decreased,particularly in unused circuitry.

According to a first aspect, there is provided a tunable inductorarrangement arrangable on a chip or substrate, the tunable inductorcomprising a first winding part connected at a first end to a firstinput of the tunable inductor arrangement; a second winding partconnected at a first end to a second end of the first winding part; athird winding part connected at a first end to a second input of thetunable inductor arrangement; a fourth winding part connected at a firstend end to a second end of the third winding part and at a second endconnected towards a second end of the second winding part; and a switcharrangement arranged to tune the tunable inductor arrangement byselectively provide at least: a circuit comprising the first and thirdwinding parts in series between the first and second inputs; and acircuit comprising the first, second, fourth and third winding parts inseries between the first and second inputs. The first and third windingparts are arranged on the chip or substrate such that magnetic fields ofthe first and third winding parts are essentially common, and the secondand fourth winding parts are arranged to cancel electro-magneticcoupling with the first and third winding parts.

The fourth winding part may be connected at the second end to the secondend of the second winding part.

The tunable inductor arrangement may comprise further winding partsconnected between the second end of the fourth winding part and thesecond end of the second winding part.

The switch arrangement may comprise a first switch connected between thesecond end of the first winding part and the second end of the thirdwinding part.

The switch arrangement may comprise a first switch connected between thesecond end of the first winding part and a virtual ground connected tothe second end of the second winding part; and a second switch connectedbetween the second end of the third winding part and the virtual ground.

The second and fourth winding parts may form a pattern on the chip orsubstrate having a first part directing the magnetic field in a firstdirection and a second part directing the magnetic field in a seconddirection, wherein the second direction is opposite to the firstdirection. The pattern of the second and fourth winding parts and thepattern of the first and third winding parts may be symmetricallyarranged on the chip or substrate. The first and third winding parts mayform a pattern encircling the second and fourth winding parts in a planeof the chip or substrate.

The pattern of the second and fourth winding parts may be eight-shaped,four-clover-shaped, or 2n-clover-shaped, where n is a positive integer.

Two or more of the winding parts may be arranged in a plurality ofconductive layers on the chip or substrate.

The virtual ground may be a DC power supply, which at AC, such as radiofrequency, acts as a ground for AC signals, or be a ground or DCreference voltage node.

According to a second aspect, there is provided a radio frequencytransceiver comprising a resonator, wherein the resonator comprises atunable inductor arrangement according to the first aspect, wherein thetunable inductor arrangement is tunable to enable the resonator toselectably work at one of a plurality of resonating frequencies.

According to a third aspect, there is provided a multiband radiofrequency receiver comprising a first receiver path arranged to receivea radio signal in a first frequency band; a second receiver patharranged to receive a radio signal in a second frequency band, whereinthe first frequency band operates at a higher frequency than the secondfrequency band, and each of the first and second receiver paths isarranged to selectively operate at a selected frequency band among aplurality of frequency bands; and comprises a resonator comprising atunable inductor arrangement according to the first aspect, whichresonator is arranged to be tuned for the selected frequency band.

According to a fourth aspect, there is provided a communication devicecomprising a radio frequency transceiver according to the second aspector a multiband radio frequency receiver according to the third aspect,and a processor arranged to interact with the radio frequencytransceiver or the multiband radio frequency receiver, wherein theprocessor is arranged to control to the switch arrangement to select atuning mode of the tunable inductor arrangement.

According to a fifth aspect, there is provided a method of a tunableinductor arrangement including winding parts and switches for tuningaccording to the first aspect. The method comprises determining a tuningsetting for the tunable inductor arrangement; assigning switch statesfor the switch or respective switches for the tuning setting; andcontrolling the switch or switches according to the assigned switchstates.

According to a sixth aspect, there is provided a computer programcomprising computer executable instructions which when executed by aprogrammable controller of a radio frequency transceiver or multibandradio frequency receiver comprising a resonator which comprises atunable inductor arrangement causes the controller to perform the methodof the fifth aspect.

An advantage is achieved for embodiments when Q-value increases withfrequency, with a layout that provides higher Q-value in low inductancestate than in high inductance state, and absolute resonator bandwidthbecomes more constant over frequency.

An advantage according to embodiments is that a tunable resonator allowsa more flexible configuration of a multi-bandreceiver/transmitter/transceiver. For example, different receiver pathsno longer need to be dedicated to either low band or high band, but canbe allocated depending on current reception situation.

Other objectives, features and advantages of the present invention willappear from the following detailed disclosure, from the attacheddependent claims as well as from the drawings. Generally, all terms usedin the claims are to be interpreted according to their ordinary meaningin the technical field, unless explicitly defined otherwise herein. Allreferences to “a/an/the [element, device, component, means, step, etc]”are to be interpreted openly as referring to at least one instance ofsaid element, device, component, means, step, etc., unless explicitlystated otherwise. The steps of any method disclosed herein do not haveto be performed in the exact order disclosed, unless explicitly stated.

BRIEF DESCRIPTION OF THE DRAWINGS

The above, as well as additional objects, features and advantages of thepresent invention, will be better understood through the followingillustrative and non-limiting detailed description of preferredembodiments of the present invention, with reference to the appendeddrawings.

FIG. 1 schematically illustrates a tunable inductor arrangementaccording to an embodiment.

FIG. 2 schematically illustrates a tunable inductor arrangementaccording to an embodiment.

FIG. 3 illustrates a layout of windings of a tunable inductorarrangement together with a schematic indication on the switcharrangement according to embodiments.

FIG. 4 illustrates a detail of a layout of windings of a tunableinductor arrangement according to an embodiment.

FIG. 5 schematically illustrates a radio front end where the tunableinductor arrangements according to embodiments are applicable.

FIG. 6 is a block diagram schematically illustrating a communicationdevice according to an embodiment.

FIG. 7 is a flow chart schematically illustrating a method of a tunableinductor arrangement according to an embodiment.

FIG. 8 schematically illustrates a computer program and a processor forimplementing the method.

DETAILED DESCRIPTION

FIG. 1 schematically illustrates a tunable inductor arrangementaccording to an embodiment. The inductor arrangement is preferablyarranged on a chip or substrate, as will be demonstrated below. Theinductor arrangement comprises a first winding part W1 connected at oneend to a first input INP of the tunable inductor arrangement, a secondwinding part W2 connected at one end to the other end of the firstwinding part W1, a third winding part W3 connected at one end to asecond input INN of the tunable inductor arrangement, and a fourthwinding part W4 connected at one end to the other end of the thirdwinding part W3 and at another end connected to the other end of thesecond winding part W2. The point where the second and fourth windingparts W2, W4 joints can optionally be connected to an AC ground, e.g. tosupply voltage, as a centre tap. A series connection of the windingparts W1, W2, W4, W3 is thus inherently formed. The tunable inductorarrangement further comprises a switch arrangement arranged to tune thetunable inductor arrangement by selectively provide either the seriesconnection or a circuit comprising the first and third winding parts W1,W3 in series between the first and second inputs INP, INN. The windingparts are arranged on a chip or substrate, i.e. essentially in oneplane, but the windings may be formed in two or more metal layers,wherein the windings can be stacked on the chip or substrate or arrangedside-by-side in a metal layer, or a combination thereof. The switcharrangement comprises a switch S12 connected between the other end ofthe first winding part W1 and the other end of the third winding partW3. When the switch S12 is open, the series connection of the windingparts W1, W2, W4, W3 is operable, while when the switch S12 is closed,the circuit comprising the first and third winding parts W1, W3 inseries is operable between the first and second inputs INP, INN. When inthe state where only the first and third winding parts W1, W3 areoperable, it is desirable that the inoperable second and fourth windingsW2, W4 do not influence, e.g. to keep insertion loss low. Therefore, thefirst and third winding parts are arranged on the chip or substrate suchthat magnetic fields of the first and third windings are essentiallycommon, and the second and fourth winding parts are arranged to cancelelectro-magnetic coupling with the first and third winding parts. Thiscan be arranged by a winding structure that cancels magnetic couplingbetween the first/third and the second/fourth windings, as will bedemonstrated by example with reference to FIG. 3 below. The principlecan be accomplished by the second and fourth winding parts form apattern on the chip or substrate having a first part directing themagnetic field in a first direction and a second part directing themagnetic field in a second direction, wherein the second direction isopposite to the first direction. The magnetic coupling is therebycancelled. It is to be noted that the centre tap is connected to thesupply node in the low-impedance mode, and when the switch S12 is closedthere are paths from the first and third windings parts W1, W3 to thecentre tap node via the short-circuited second and fourth winding partsW2, W4. The impedance or resistance is reasonably increased, but isproviding a working solution for many applications.

FIG. 2 schematically illustrates a tunable inductor arrangementaccording to an embodiment. The inductor arrangement is preferablyarranged on a chip or substrate, as will be demonstrated below. Theinductor arrangement comprises a first winding part W1 connected at oneend to a first input INP of the tunable inductor arrangement, a secondwinding part W2 connected at one end to the other end of the firstwinding part W1, a third winding part W3 connected at one end to asecond input INN of the tunable inductor arrangement, and a fourthwinding part W4 connected at one end to the other end of the thirdwinding part W3 and at another end connected to the other end of thesecond winding part W2. The point where the second and fourth windingparts W2, W4 joints is connected to an AC ground, e.g. to supplyvoltage, as a centre tap. A series connection of the winding parts W1,W2, W4, W3 is thus inherently formed. The tunable inductor arrangementfurther comprises a switch arrangement arranged to tune the tunableinductor arrangement by selectively provide either the series connectionor a circuit comprising the first and third winding parts W1, W3 inseries between the first and second inputs INP, INN. The winding partsare arranged on a chip or substrate, i.e. essentially in one plane, butthe windings may be formed in two or more metal layers, wherein thewindings can be stacked on the chip or substrate or arrangedside-by-side in a metal layer, or a combination thereof. The switcharrangement comprises a first switch S1 connected between the other endof the first winding part W1 and the AC ground, i.e. to the centre tap.A second switch S2 is connected between the centre tap and the other endof the third winding part W3. When the switches S1 and S2 are open, theseries connection of the winding parts W1, W2, W4, W3 is operable, whilewhen the switches S1 and S2 are closed, the circuit comprising the firstand third winding parts W1, W3 in series is operable between the firstand second inputs INP, INN. The AC connection provided in the open stateby the centre tap is in the closed state still provided via the switchesS1, S2. Here, the dual switch arrangement provides a lower impedancepath to the centre tap compared to the embodiment demonstrated withreference to FIG. 1, but may be to a cost of higher parasiticcapacitances. When in the state where only the first and third windingparts W1, W3 are operable, it is desirable that the inoperable secondand fourth windings W2, W4 do not influence, e.g. to keep insertion losslow. Therefore, the first and third winding parts are arranged on thechip or substrate such that magnetic fields of the first and thirdwindings are essentially common, and the second and fourth winding partsare arranged to cancel electro-magnetic coupling with the first andthird winding parts. This can be arranged by a winding structure thatcancels magnetic coupling between the first/third and the second/fourthwindings, as will be demonstrated by example with reference to FIG. 3below. The principle can be accomplished by the second and fourthwinding parts form a pattern on the chip or substrate having a firstpart directing the magnetic field in a first direction and a second partdirecting the magnetic field in a second direction, wherein the seconddirection is opposite to the first direction. The magnetic coupling isthereby cancelled. By using two switches S1, S2 connected to the centretap, lower impedance connection to the supply node is achieved, whichmay be important for some applications. On the other hand, the morecomplex switch arrangement may result in more parasitic resistanceand/or capacitance, which may degrade resonator performance in someapplications.

FIG. 3 illustrates an example of layout of windings of a tunableinductor arrangement together with a schematic indication on the switcharrangement according to embodiments, where the respective switcharrangements demonstrated with reference to FIGS. 1 and 2 areschematically illustrated in FIG. 3. The first and third winding partsform a pattern encircling the second winding in a plane of the chip orsubstrate. The pattern of the second and fourth winding parts and thepattern of the first and third winding parts are symmetrically arrangedon the chip or substrate, as emphasized by symmetry lines provided inFIG. 3. The pattern of the second and fourth winding parts iseight-shaped in FIG. 3, which provides for a first part directing themagnetic field in a first direction and a second part directing themagnetic field in a second direction, wherein the second direction isopposite to the first direction. Other patterns providing the sameeffect are equally possible, e.g. four-clover-shaped, or2n-clover-shaped, where n is a positive integer.

FIG. 4 illustrates a detail of an example of layout of windings of atunable inductor arrangement according to an embodiment. Crossings ofconductive lanes forming the windings can thus be achieved. Two or moreof the winding parts can be arranged in a plurality of conductive layerson the chip or substrate. In the illustrations, the lanes are providedside by side on the substrate and the crossings using layeredconductors. However, the lanes can also use layered conductors and beplaced on top of each other, or a combination of be provided indifferent layers and side by side. The shape of the windings have alsobeen illustrated as octagons, but other shapes are as feasible, such ascircular, square, or other n-sided shape, where n is 3 or higher, orcombinations thereof, which form windings enclosing a magnetic fieldwhich is the purpose of the windings to form an inductance. Theinductance can be adapted for differential purposes or single-endedpurposes in conventional way.

Further winding parts can be connected between the second and fourthwinding parts W2, W4, which can be included in forming a circuit of thetunable inductor arrangement. Such further winding parts are preferablyalso arranged on the chip or substrate such that magnetic fields forcancelling electro-magnetic coupling with the first to fourth windingparts W1-W4 similar to the relation between the second and fourthwinding parts W2, W4 to the first and third winding parts W1, W3. Thiscan be enabled by applying further metal layers for implementing thewinding parts on the chip or substrate, and further switches of theswitch arrangement for selectively provide circuits including a desiredamount of winding parts.

FIG. 5 schematically illustrates a radio front end where the tunableinductor arrangements according to embodiments are applicable. In aradio front end circuit used for example in a 3GPP LTE radio, amultitude of bands may be used. Further, if for example carrieraggregation where separate bands are collected and used simultaneouslyin different configurations, versatility is a key to a feasible frontend solution. Still further, if the front end should be usable for otherradio access technologies as well, such as GSM, UMTS, WLAN, GNSS, etc.,the demands on versatility further increases. The received signal canthus be in a multitude of frequencies and having wide or narrowbandwidth, and for example a band selection filter, or other circuitthat need a resonator, may need to be configurable for this depending oncurrent operating mode. Variable capacitance in such band selectionfilters normally do a lot, e.g. by using capacitor banks wherecapacitance can be switched in on demand, but by using a tunableinductor as demonstrated above, versatility can be improved, as well asperformance of for example the band selection filters. By using one ormore tunable inductor arrangements 502, 504 as those demonstrated above,the demands on versatility can be met. Flexible band combinations arethereby enabled.

An example where the front end arrangement as demonstrated above can beused is a multiband radio frequency receiver 500. The receiver 500comprises a first receiver path arranged to receive a radio signal in afirst frequency band and a second receiver path arranged to receive aradio signal in a second frequency band, wherein the first frequencyband operates at a higher frequency than the second frequency band, i.e.a high-low band arrangement where both the high and the low bands can bereceived simultaneously. Each of the first and second receiver paths canbe arranged to selectively operate at a selected frequency band among aplurality of frequency bands, e.g. the first high-band path can selectto operate in one of 1800 MHz, 1900 MHz, 2100 MHz and 2700 MHz frequencybands while the second low-band path can select to operate in one of 750MHz, 850 MHz, 900 MHz and 1500 MHz frequency bands simultaneously. Thesefrequency bands are only demonstrated as examples, and other frequencybands and groupings between high and low frequency bands are equallypossible. Each receiver path comprises a resonator comprising a tunableinductor arrangement 502, 504 as demonstrated above, wherein theresonators are arranged to be tuned for the selected frequency band inrespective receiver path. It is to be noted that both receiver paths aretunable to all frequency bands by the approach of the tunable inductorarrangement, wherein great flexibility is achieved since there is nodedicated path for the higher or lower bands. Arrangements with morethan two such receiver paths are also possible. Flexible frequency bandcombinations are thus enabled, which for example is advantageous incarrier aggregation solutions.

In FIG. 5, the resonators are illustrated for tuning LNA outputs as anexample. The resonator with tunable inductor arrangement can of coursebe used for other purposes as well, such as for filters, impedancematching, etc.

FIG. 6 is a block diagram schematically illustrating communicationdevice 600 according to an embodiment. The communication devicecomprises a receiver or transceiver 602, which can be connected to anantenna 604, and other circuits 606 such as a processor arrangedinteract with the receiver or transceiver 602, input and outputinterfaces of the communication device 600, etc. The receiver ortransceiver 602 comprises a resonator 610, wherein the resonatorcomprises a tunable inductor arrangement according to any one ofembodiments demonstrated above, wherein the tunable inductor arrangementis tunable to enable the resonator 610 to work at a plurality ofresonating frequencies. The receiver or transceiver can also comprise acontroller 608 which can be arranged to control the tuning of theresonator 610, i.e. also the tunable inductor arrangement. The receiver602 can for example be the multiband radio frequency receiver 500demonstrated with reference to FIG. 5.

FIG. 7 is a flow chart schematically illustrating a method of a tunableinductor arrangement according to an embodiment. The method comprisesdetermining 701 a tuning setting for the tunable inductor arrangement.This can be made by receiving frequency allocation from a remote entityor from an entity within a communication apparatus having the tunableinductor arrangement. Based on for example the frequency allocationinformation switch states are assigned 702 for the switch S12 orrespective switches S1, S2 for the tuning setting, and controlling 703the switches according to the assigned switch states. Upon a newallocation, the procedure can be repeated.

The method according to the present invention is suitable forimplementation with aid of processing means, such as computers and/orprocessors, especially for the case where a digital controller controlsthe transceiver. Therefore, there is provided computer programs,comprising instructions arranged to cause the processing means,processor, or computer to perform the steps of any of the methodsaccording to any of the embodiments described with reference to FIG. 7.The computer programs preferably comprises program code which is storedon a computer readable medium 800, as illustrated in FIG. 8, which canbe loaded and executed by a processing means, processor, or computer 802to cause it to perform the methods, respectively, according toembodiments of the present invention, preferably as any of theembodiments described with reference to FIG. 7. The computer 802 andcomputer program product 800 can be arranged to execute the program codesequentially where actions of the any of the methods are performedstepwise. The processing means, processor, or computer 802 is preferablywhat normally is referred to as an embedded system. Thus, the depictedcomputer readable medium 800 and computer 802 in FIG. 8 should beconstrued to be for illustrative purposes only to provide understandingof the principle, and not to be construed as any direct illustration ofthe elements.

The invention has mainly been described above with reference to a fewembodiments. However, as is readily appreciated by a person skilled inthe art, other embodiments than the ones disclosed above are equallypossible within the scope of the invention, as defined by the appendedpatent claims.

The invention claimed is:
 1. A tunable inductor arrangement arrangeableon a chip or substrate, the tunable inductor arrangement comprising: atunable inductor comprising: a first winding part connected at a firstend to a first input of the tunable inductor arrangement; a secondwinding part connected at a first end to a second end of the firstwinding part; a third winding part connected at a first end to a secondinput of the tunable inductor arrangement; a fourth winding partconnected at a first end to a second end of the third winding part andat a second end connected towards a second end of the second windingpart; and a switch arrangement arranged to tune the tunable inductorarrangement by selectively providing at least: a circuit comprising thefirst and third winding parts in series between the first and secondinputs; and a circuit comprising the first, second, fourth and thirdwinding parts in series between the first and second inputs; wherein thefirst and third winding parts are arranged on the chip or substrate suchthat magnetic fields of the first and third winding parts areessentially common; and the second and fourth winding parts form apattern on the chip or substrate having a first part directing themagnetic field in a first direction and a second part directing themagnetic field in a second direction, wherein the second direction isopposite to the first direction.
 2. The tunable inductor arrangement ofclaim 1, wherein the fourth winding part is connected at the second endto the second end of the second winding part.
 3. The tunable inductorarrangement of claim 1, comprising further winding parts connectedbetween the second end of the fourth winding part and the second end ofthe second winding part.
 4. The tunable inductor arrangement of claim 1,wherein the switch arrangement comprises a first switch connectedbetween the second end of the first winding part and the second end ofthe third winding part.
 5. The tunable inductor arrangement of claim 1,wherein the switch arrangement comprises a first switch connectedbetween the second end of the first winding part and a virtual groundconnected to the second end of the second winding part; and a secondswitch connected between the second end of the third winding part andthe virtual ground.
 6. The tunable inductor arrangement of claim 1,wherein the pattern of the second and fourth winding parts and thepattern of the first and third winding parts are symmetrically arrangedon the chip or substrate.
 7. The tunable inductor arrangement of claim6, wherein the pattern of the second and fourth winding parts iseight-shaped, four-clover-shaped, or 2n-clover-shaped, where n is apositive integer.
 8. The tunable inductor arrangement of claim 1,wherein the first and third winding parts form a pattern encircling thesecond and fourth winding parts in a plane of the chip or substrate. 9.The tunable inductor arrangement of claim 1, wherein two or more of thewinding parts are arranged in a plurality of conductive layers on thechip or substrate.
 10. A radio frequency transceiver comprising aresonator, wherein the resonator comprises the tunable inductorarrangement of claim 1, wherein the tunable inductor arrangement istunable to enable the resonator to selectably work at one of a pluralityof resonating frequencies.
 11. A communication device comprising theradio frequency transceiver of claim 10, and a processor arranged tointeract with the radio frequency transceiver, wherein the processor isarranged to control to the switch arrangement to select a tuning mode ofthe tunable inductor arrangement.
 12. A multiband radio frequencyreceiver comprising: a first receiver path arranged to receive a radiosignal in a first frequency band; and a second receiver path arranged toreceive a radio signal in a second frequency band; wherein the firstfrequency band operates at a higher frequency than the second frequencyband; and wherein each of the first and second receiver paths isarranged to selectively operate at a selected frequency band among aplurality of frequency bands and comprises a resonator comprising thetunable inductor arrangement of claim 1, which resonator is arranged tobe tuned for the selected frequency band.
 13. A communication devicecomprising the multiband radio frequency receiver of claim 12, and aprocessor arranged to interact with the multiband radio frequencyreceiver, wherein the processor is arranged to control to the switcharrangement to select a tuning mode of the tunable inductor arrangement.